Download or read book Seismic Perspectives from the Western U S on Magma Reservoirs Underlying Large Silicic Calderas written by Brandon Schmandt and published by . This book was released on 2019 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since 1.25 Ma, three volcanic systems in the western U.S. Cordillera hosted rhyolitic eruptions of greater than or equal to 300 km3 dense rock equivalent creating the Yellowstone (0.63 Ma), Long Valley (0.76 Ma), and Valles (1.25 Ma) calderas. Their similar time scales since caldera-forming eruptions and rich histories of seismic research motivate a review of seismic constraints on the modern magma reservoirs beneath these calderas from the uppermost mantle to the upper crust. Across the Cordillera upper mantle seismic velocities are generally below the continental average and each of the calderas is underlain by exceptionally low velocities consistent with the presence of mantle melt, greater than or equal to 3%. Concentrated upper mantle low-velocity anomalies are found beneath the eastern Snake River plain southwest of Yellowstone caldera and beneath Long Valley caldera. Valles caldera is located above a broadly distributed low-velocity anomaly associated with the Rio Grande Rift and Jemez volcanic lineament. At lower crustal depths potential magma reservoirs exhibit weaker seismic velocity anomalies and greater variability among the results of different tomographic inversion methods compared to shallower depths. At middle-to-upper crustal depths, ~5?15 km, seismic tomography provides evidence of magmatic reservoirs beneath all three calderas, and scattered wave imaging supports sharp upper, lateral, and/or lower boundaries of each inferred magma reservoir. Estimates of average melt fractions in these reservoirs vary from ~9?23% based on recent tomography, with localized melt fraction estimates as high as ~30?60% based on sharp interfaces detected by scattering and ray bending analyses. The wide range of inferred melt fractions likely results from contrasting sensitivities of different seismic imaging methods combined with spatially heterogeneous melt fractions and uncertainties in mapping seismic velocities to silicate melt fractions. Seismic radial anisotropy beneath Yellowstone and Long Valley calderas indicates that middle-to-upper crustal reservoirs are organized as sill complexes with relatively crystal-poor and crystal-rich layers, suggesting magma storage in many weakly connected volumes. Future estimates of (an)isotropic seismic velocities and melt fractions across 3D reservoirs may be improved through expanded applications of full waveform tomography to body and surface waves and increasingly dense array studies facilitated by combinations of broadband and rapidly-deployable shorter-period seismographs. Advanced seismic imaging offers potential for improved delineation of magma reservoir boundaries and constraints on intra-reservoir structures such as sill complexes that provide insight into magma reservoir mechanics and compositional heterogeneity.
Download or read book Seismically Anisotropic Magma Reservoirs Underlying Silicic Calderas cJiang Chengxin Brandon Schmandt Jamie Farrell Fan Chi Lin and Kevin M Ward written by Chengxin Jiang and published by . This book was released on 2018 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seismic anisotropy can illuminate structural fabrics or layering with length scales too ne to be resolved as distinct features in most seismic tomography. Radial anisotropy, which detects differences between horizontally (V sh) and vertically (V sv) polarized shear wave velocities, was investigated beneath Yellowstone caldera (Wyoming, United States) and Long Valley caldera (California). Signifcant positive radial anisotropy indicating V sh > V sv and low isotropic velocities, were found beneath both calderas at ~5?18 km depths. The positive radial anisotropy (>8%) volumes beneath the calderas are anomalously strong compared to the surrounding areas. The absence of a similar anisotropic signal in the wake of the propagating Yellowstone hotspot indicates that the radial anisotropy diminishes after the locus of voluminous silicic magmatism moves. We propose that the anisotropic volumes represent sill complexes of compositionally evolved magma, and the magma?s seismic contrast with the crust would largely fade upon crystallization. The similarity of magma reservoir anisotropy in varied tectonic settings suggests that such mid-crustal sill complexes may be ubiquitous features of silicic caldera?forming magmatic systems, and that anisotropy should be considered to seismically estimate melt content and mobility. The absence of similar radial anisotropy in the lower crust beneath the calderas suggests lower melt fractions or a transition in the geometry of magma pathways.
Download or read book Historical unrest at the large calderas of the world written by Christopher G. Newhall and published by . This book was released on 1988 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Volcanoes written by John P. Lockwood and published by John Wiley & Sons. This book was released on 2013-04-26 with total page 677 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volcanoes are essential elements in the delicate global balance of elemental forces that govern both the dynamic evolution of the Earth and the nature of Life itself. Without volcanic activity, life as we know it would not exist on our planet. Although beautiful to behold, volcanoes are also potentially destructive, and understanding their nature is critical to prevent major loss of life in the future. Richly illustrated with over 300 original color photographs and diagrams the book is written in an informal manner, with minimum use of jargon, and relies heavily on first-person, eye-witness accounts of eruptive activity at both "red" (effusive) and "grey" (explosive) volcanoes to illustrate the full spectrum of volcanic processes and their products. Decades of teaching in university classrooms and fieldwork on active volcanoes throughout the world have provided the authors with unique experiences that they have distilled into a highly readable textbook of lasting value. Questions for Thought, Study, and Discussion, Suggestions for Further Reading, and a comprehensive list of source references make this work a major resource for further study of volcanology. Volcanoes maintains three core foci: Global perspectives explain volcanoes in terms of their tectonic positions on Earth and their roles in earth history Environmental perspectives describe the essential role of volcanism in the moderation of terrestrial climate and atmosphere Humanitarian perspectives discuss the major influences of volcanoes on human societies. This latter is especially important as resource scarcities and environmental issues loom over our world, and as increasing numbers of people are threatened by volcanic hazards Readership Volcanologists, advanced undergraduate, and graduate students in earth science and related degree courses, and volcano enthusiasts worldwide. A companion website is also available for this title at www.wiley.com/go/lockwood/volcanoes
Download or read book Investigations of Magmatic End members written by Gwyneth Retta Hughes and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Approximately 10% of the global population, some 550 million people, live within 100 km of an active volcano, making it imperative that the causes of magma accumulation in the crust and the factors affecting the scale of subsequent volcanic eruptions are investigated and modeled. This PhD dissertation examines magmatic processes at two scales: silicic calderas represent the large but infrequent end of the continuum, whereas mafic dikes are small in scale but common. Many previous authors have presented hypotheses for how large silicic systems develop. In order to test and refine these hypotheses, I undertook a global compilation that empirically examines how the characteristics of 140 young silicic calderas reflect their crustal-tectonic setting. Results indicate that the size and geochemistry of silicic calderas are affected by the nature of the underlying crust, the tectonic setting, and the local stress regime. For example, large, rhyolitic calderas tend to occur in continental settings under extension. There are, however, few true "rules, " and exceptions may prove useful in analyzing how silicic magma chambers form. Based on this compilation, I present a probabilistic method for determining the tectonic-crustal setting of a given caldera from its diameter, and eruption geochemistry. Focusing specifically on arc settings, this study demonstrates that (1) the abundance of silicic calderas in a given arc is proportional to the trench-normal convergence rate, except in arcs with back-arc spreading; and (2) silicic calderas in continental arcs tend to occur farther behind the volcanic front than do more typical arc volcanoes, possibly because of the abundance of pre-existing structures in continental margins. At the opposite end of the volcanic spectrum, this dissertation examines the intrusion of two mafic dikes. The first lies beneath Mammoth Mountain, California, and was associated with a 1989 seismic swarm. Based on an inversion of leveling data constrained by relocated earthquakes, I propose that a dike 2 km long, 8 km high, with 1 m of opening was intruded at 9 km depth beneath the south side of Mammoth Mountain. The second dike investigation focused on the eruption of Miyakejima, Japan, in 2000, associated with more than 10,000 earthquakes, several small eruptions and progressive caldera collapse. Displacements recorded by GPS stations and pre- and syn- event seismicity were used to determine a geological explanation of the event. In the proposed model, a shallow dike propagated ~30 km away from Miyakejima for one week, stopped propagating laterally after intersecting a pre-existing fault zone, and then continued to open and grow vertically for nearly two months.
Download or read book Tomography from 26 Years of Seismicity Revealing that the Spatial Extent of the Yellowstone Crustal Magma Reservoir Extends Well Beyond the Yellowstone Caldera written by Jamie Mark Farrell and published by . This book was released on 2014 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Yellowstone volcanic field has experienced three of Earth's most explosive volcanic eruptions in the last 2.1 Ma. The most recent eruption occurred 0.64 Ma forming the 60 km long Yellowstone caldera. We have compiled earthquake data from the Yellowstone Seismic Network from 1984 to 2011 and tomographically imaged the three-dimensional P wave velocity (Vp) structure of the Yellowstone volcanic system. The resulting model reveals a large, low Vp body, interpreted to be the crustal magma reservoir that has fueled Yellowstone's youthful volcanism. Our imaged magma body is 90 km long, 5-17 km deep, and 2.5 times larger than previously imaged. The magma body extends ~15 km NE of the caldera and correlates with the location of the largest negative gravity anomaly, a -80 mGal gravity low. This new seismic image provides important constraints on the dynamics of the Yellowstone magma system and its potential for future volcanic eruptions and earthquakes.
Download or read book Magmatic Systems written by Michael P. Ryan and published by Academic Press. This book was released on 1994-08-26 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: With its integrated and cohesive coverage of the current research, Magmatic Systems skillfully explores the physical processes, mechanics, and dynamics of volcanism. The text utilizes a synthesized perspective--theoretical, experimental, and observational--to address the powerful regulatory mechanisms controlling the movement of melts and cooling, with emphasis on mantle plumes, mid-ocean ridges, and intraplate magmatism. Further coverage of subduction zone magmatism includes:Fluid mechanics of mixed magma migrationInternal structure of active systemsGrain-scale melt flowRheology of partial meltsNumerical simulation of porous media melt migrationNonlinear (chaotic and fractal) processes in magma transportIn all, Magmatic Systems will prove invaluable reading to those in search of an interdisciplinary perspective on this active topic. Key Features* Fluid mechanics of magma migration from surface region to eruption site* Internal structure of active magmatic systems* Grain-scale melt flow in mantle plumes and beneath mid-ocean ridges* Physics of magmatic systems and magma dynamics
Download or read book Volcanic Eruptions and Their Repose Unrest Precursors and Timing written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2017-07-24 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volcanic eruptions are common, with more than 50 volcanic eruptions in the United States alone in the past 31 years. These eruptions can have devastating economic and social consequences, even at great distances from the volcano. Fortunately many eruptions are preceded by unrest that can be detected using ground, airborne, and spaceborne instruments. Data from these instruments, combined with basic understanding of how volcanoes work, form the basis for forecasting eruptionsâ€"where, when, how big, how long, and the consequences. Accurate forecasts of the likelihood and magnitude of an eruption in a specified timeframe are rooted in a scientific understanding of the processes that govern the storage, ascent, and eruption of magma. Yet our understanding of volcanic systems is incomplete and biased by the limited number of volcanoes and eruption styles observed with advanced instrumentation. Volcanic Eruptions and Their Repose, Unrest, Precursors, and Timing identifies key science questions, research and observation priorities, and approaches for building a volcano science community capable of tackling them. This report presents goals for making major advances in volcano science.
Download or read book Geologic Field trip Guide to the Volcanic and Hydrothermal Landscape of the Yellowstone Plateau written by Lisa A. Morgan and published by Government Printing Office. This book was released on 2017 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Seismic Wave Propagation in Stratified Media written by Brian Kennett and published by ANU E Press. This book was released on 2009-05-01 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seismic Wave Propagation in Stratified Media presents a systematic treatment of the interaction of seismic waves with Earth structure. The theoretical development is physically based and is closely tied to the nature of the seismograms observed across a wide range of distance scales - from a few kilometres as in shallow reflection work for geophysical prospecting, to many thousands of kilometres for major earthquakes. A unified framework is presented for all classes of seismic phenomena, for both body waves and surface waves. Since its first publication in 1983 this book has been an important resource for understanding the way in which seismic waves can be understood in terms of reflection and transmission properties of Earth models, and how complete theoretical seismograms can be calculated. The methods allow the development of specific approximations that allow concentration on different seismic arrivals and hence provide a direct tie to seismic observations.
Download or read book Volcanic Unrest written by Joachim Gottsmann and published by Springer. This book was released on 2018-12-18 with total page 313 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book summarizes the findings of the VUELCO project, a multi-disciplinary and cross-boundary research funded by the European Commission's 7th framework program. It comprises four broad topics: 1. The global significance of volcanic unrest 2. Geophysical and geochemical fingerprints of unrest and precursory activity 3. Magma dynamics leading to unrest phenomena 4. Bridging the gap between science and decision-making Volcanic unrest is a complex multi-hazard phenomenon. The fact that unrest may, or may not lead to an imminent eruption contributes significant uncertainty to short-term volcanic hazard and risk assessment. Although it is reasonable to assume that all eruptions are associated with precursory activity of some sort, the understanding of the causative links between subsurface processes, resulting unrest signals and imminent eruption is incomplete. When a volcano evolves from dormancy into a phase of unrest, important scientific, political and social questions need to be addressed. This book is aimed at graduate students, researchers of volcanic phenomena, professionals in volcanic hazard and risk assessment, observatory personnel, as well as emergency managers who wish to learn about the complex nature of volcanic unrest and how to utilize new findings to deal with unrest phenomena at scientific and emergency managing levels. This book is open access under a CC BY license.
Download or read book Eruptive History and Chemical Evolution of the Precaldera and Postcaldera Basalt dacite Sequences Long Valley California written by Roy A. Bailey and published by . This book was released on 2004 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanisms of Activity and Unrest at Large Calderas written by Claudia Troise and published by Geological Society of London. This book was released on 2006 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: Large caldera collapses represent catastrophic natural events, second only to large meteoritic impacts. In addition, some calderas are densely populated, making the risk extreme, even for moderate eruptions. Understanding caldera mechanisms, unrest and the danger of eruption is therefore a crucial challenge for Earth sciences. Several key features of caldera behaviour have yet to be fully understood. Through a combination of case studies and theoretical modelling, the following topics are addressed in this volume: the conditions required to produce and to release large volumes of magma erupted during caldera formation; how magmatic feeding systems evolve before and after a caldera has formed; the processes that limit the behaviour of precursors to eruptions; how pre-eruptive precursors can be distinguished from those that drive unrest without an eruption; and given that post-collapse eruptions may occur across a wide area, the optimum procedures for designing hazard maps and mitigation strategies.
Download or read book Magmatic Processes in a Silicic Caldera forming System written by Clara Waelkens and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Large, silicic, caldera-forming eruptions are infrequent, but their impact on humans and their environment can be dramatic. This emphasises the importance of a good understanding of these so-called “supervolcanic” systems and of the processes that take place in their magma chambers. Valles caldera is an ideal system in which to study these processes; its continuous sequence of eruptions provides a window into both the magma chamber primed for eruption, and into the re-establishment of the magma chamber between two super-eruptions.Volatiles play a key role in magma chambers, both as dissolved species in the melt and in exsolved vapour phases. In this thesis, I measured halogen, H2O and CO2 concentrations in melt inclusions from the Lower Bandelier Tuff (LBT), Upper Bandelier Tuff (UBT), the Valle Toledo Member (VTM) rhyolites in between, and the Deer Canyon Rhyolites at the end of the UBT sequence, in order to reconstruct volatile evolution in the Bandelier magmatic system. By comparing the behaviour of fluorine, chlorine and bromine in the eruption sequence, I concluded that large masses of Cl and Br were fractionated from the magma to a separate exsolved fluid phase. While syn-eruptive degassing of halogens was negligible in both the LBT and the UBT eruptions, the fluid phase released 4800 Tg of Cl and 5.7 Tg of Br to the atmosphere during the LBT eruption, and 2090 Tg Cl and 3.6 Tg Br in the UBT eruption. This implies the Bandelier eruptions had a severe impact on the chemistry of the paleo-atmosphere, particularly on the ozone layer.Three sharp increases to higher CO2 concentrations are recorded in the Bandelier sequence: (1) in the LBT plinian, where dissolved CO2 concentrations increase from a mean value of 27 ppm at the base of the plinian to 173 ppm in the mid-plinian; (2) in VTM group III, which at a mean of 197 ppm exhibit the highest CO2 concentrations of the entire sequence; and (3) in the UBT plinian,where CO2 concentrations increase from a mean of 54 ppm at the base of the plinian to 101 ppm in the mid-plinian. I interpret these sharp increases as the result of the injection of fresh magma into the chamber, with CO2-rich vapours that exsolved from the recharge magma percolating through the magma chamber and increasing CO2 concentrations.In a departure from volatiles, I finally focused on the importance of recharge events into the Valles caldera system. Prompted by the suggestion in previous studies that a series of hornblende-rich dacite pumices in the early-erupted UBT are related to the pre-caldera, intermediate composition Tschicoma Formation, I performed a geochemical study of the Tschicoma lava dome and lava flow complexes. Through major, trace element and isotopic analyses, I identified different evolutionary trends, which through different combinations of fractional crystallisation, assimilation of crustal material and magma mixing led to the geochemical diversity observed today. By relating the geochemistry of the Tschicoma domes to that of the dacite pumices in the UBT, I propose that a more mafic, possibly andesitic, parental magma to the Tschicoma dacites was injected into the UBT magma chamber, where it mixed with the resident UBT rhyolite magma to form the hornblende-rich dacite pumices"--
Download or read book Tectonic and Magmatic Evolution of the Snake River Plain Volcanic Province written by Bill Bonnichsen and published by Idaho Geological Survey. This book was released on 2002 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Geology of Mount Desert Island written by F. Bascom and published by . This book was released on 1919 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Quaternary and Pliocene Yellowstone Plateau Volcanic Field of Wyoming Idaho and Montana written by Robert L. Christiansen and published by . This book was released on 2001 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
